Electrical switch



April 8,1969 MMBBET 3,437,973

ELECTRICAL SWITCH FiIedMarch 15, 1967 1 NVENTOR JOHN C. MABBETT math .ATTORNEY United States Patent 3,437,973 ELECTRICAL SWITCH John C.Mabbett, Hollywood, Calif., assignor to Crosby Research, Inc., LosAngeles, Calif., a corporation of California Filed Mar. 15, 1967, Ser.No. 623,445 Int. Cl. H01c 9/06 US. Cl. 338-99 7 Claims ABSTRACT OF THEDISCLOSURE A pair of switch contact elements are formed on the surfaceof a first substrate member, each of such elements having a plurality offinger portions. The finger portions of the switch contact elements areinterleaved with each other. Contact bridging elements are formed on thesurface of a second substrate member. The two substrate members areplaced against each other with the bridging elements making lightsurface contact with the switch contact elements. When pressure isapplied to bring the bridging element into intimate contact with theswitch contact elements, a low resistance electrical path is providedbetween the switch contact elements.

This invention relates to an electrical switch and more particularly tosuch a switch providing momentary electrical contact in response to thetouch of the operator. Switches which respond to momentary contactpressure, which are often known as touch switches and which generallyoperate in conjunction with latching devices of the electronic orelectromechanical variety, are used extensively for normal switchingoperations as well as in warning devices such as burgular alarms and thelike. In most of such devices of the prior art, a pair of switchingcontact elements are utilized which are physically separated from eachother by a resilient separator device such as a spring or a rubber likematerial, the switch being closed by bringing the two switch contactelements into close contact with each other. Such devices often lack theeconomy of construction to be desired. Further, it is sometimesdiflicult to obtain a very high degree of sensitivity to the touchcompatible with immunity from erroneous actuation by ambient vibrationsand the like.

The device of this invention provides a simple and highly economicaltouch switch device of extremely high sensitivity to the touch yetsubstantially non-responsive to ambient vibrations, thus providing asignificant improvement over prior art touch switches.

Briefly described, the device of the invention is formed from a firstunit comprising a substrate member having a broad surface on whichelectrically conductive switch contact elements are formed, and a secondunit comprising a substrate member having a broad surface on whichelectrically conductive switch contact bridging elements are formed. Theswitch contact elements of the first unit have finger portions whichinterleave with each other. The aforementioned broad surface of thesecond substrate member is placed against the aforementioned broadsurface of the first member with the bridging elements in light surfacecontact across the finger portions of the switch contact elements. Whenpressure is applied to bring the bridging elements into intimate contactwith the contact element finger portions,- the switching action isachieved.

It is therefore an object of this invention to provide an improvedmomentary contact electrical switch.

It is therefore an object of this invention to provide an momentarycontact touch switch of highly economical construction.

It is still another object of this invention to provide a momentarycontact touch switch which has high sensitivity and which issubstantially immune to extraneous vibration signals.

Other objects of this invention will become apparent from the followingdescription taken in connection with the accompanying drawings, ofwhich:

FIG. 1 is a perspective view of one embodiment of the device of theinvention.

FIG. 2 is an exploded view showing the two component units of theembodiment of FIG. 1,

FIG. 3 is a top plan view of the unit carrying the bridging elements ofthe embodiment of FIG. 1,

FIG. 4 is a side elevation view of the unit shown in FIG. 3,

FIG. 5 is an end elevation view of the unit shown in FIG. 3,

FIG. 6 is a top plan view with partial cutaway section of the embodimentof FIG. 1, and

FIG. 7 is a cross sectional view taken along the plane indicated by 77in FIG. 6.

:Referring now to the figures, formed on the surface 11a 2 of substrateunit 11, which is fabricated of an electrically insulating material suchas a suitable plastic, are electrically conductive switch contactelements 12 and 13. Contact elements 12 and 13 which may be formed byetched circuit board techniques or by electrodeposition, preferably areof copper with a flashed gold surface. Switch contact elements 12 and 13include bar portions 12a and 13a from which extend a plurality of fingerportions 12b and 13b respectively. Finger portions 12b and 13b areinterleaved with each other. The bars and finger portions of contactelements 12 and 13 while in close proximity to each other make neitherphysical nor electrical contact. Connected to bar portion 12a and 13arespectively are lead wires 15 and 16 which carry the switching signalto the circuits being controlled, when switching is accomplished as tobe explained hereinafter.

Substrate unit 20 has a plurality of electrically conductive contactbridging elements 21 formed in the broad surface 20a thereof. Bridgingelements 21 may be formed in the same manner as contact elements 12 and13, by etched circuit board techniques or electrodeposition. Thesebridging elements are also preferably fabricated of a highly conductivematerial, such as copper with a flashed gold surface. Substrate unit 20is preferably fabricated of a flexible electrically insulating materialsuch as a suitable resilient plastic and is segmented by longitudinalslots 23 and transverse slots 24 which provide a separation between theindividual bridging elements 21 and give these elements someindependence of motion relative to each other. This provides asignificant advantage in that it enables reliable switch operation inresponse to light finger pressure on any portion of the switch operatingsurface 26, this by virtue of the fact that the individual bridgingelements 21 are not significantly restrained in their motion by theadjoining portions of unit 20.

In the fully assembled device, the broad surfaces 11a and 20a of units11 and 20 are placed against each other with bridging elements 21bridging adjoining finger portions 12b and 13b. While there is lightsurface contact between the bridging element and the finger portions,this affords only an extremely high resistance electrical path betweenfinger portions 12b and 13b, thus not permitting any significantelectrical current flow therebetween. It is to be noted that there maybe a very small separation between the opposing surfaces of thesubstrate members in the construction of the assembled unit but thatsuch actual physical separation is not necessary to the proper operationof the device.

Substrate units 11 and 20 are encapsulated in a jacket 30 which may befabricated of a suitable flexible material such as a resilient plastic.

The switch is actuated by the application of a small amount of pressureon any portion of surface 26 which brings one or more of bridgingelements 21 into intimate bridging contact with a pair of fingers 12band 13b, thereby providing the desired momentary electrical path.

The switching units 11 and 20 can readily be manufactured by massproduction techniques, such units being fabricated in a large sheetwhich then can be cut up to form the units for individual switches. Thismakes for great economy of fabrication. The individutl switches can alsobe of relatively small size and by virtue of their completeencapsulation are substantially moisture proof. This type of switchingdevice is primarily designed to provide a current path in a relativelylow voltage low current circuit which may if so desired be utilized tocontrol a high voltage high current device.

The device of this invention thus provides a simple highly economicalmomentary contact touch switch which has high touch sensitivity combinedwith high reliability of operation.

While the device of the invention has been described and illustrated indetail, it is to be clearly understood that this is intended by way ofillustration and example only and is not to be taken by way oflimitation, the spirit and scope of this invention being limited only bythe terms of the following claims.

I claim:

1. An electrical switching comprising:

a first unit comprising an electrically insulating substrate member,said first unit having a broad surface with a plurality of electricallyconductive bridging elements formed thereon, and

a second unit comprising an electrically insulating substrate member,said second unit having a broad surface with a pair of electricallyconductive switch contact elements formed thereon, said switch contactelements each comprising a bar portion with a plurality of fingerportions extending therefrom,

said first and second units being assembled to form an integral switchassembly with said aforementioned broad surfaces opposite each other andwith said bridging elements of said first unit substantially in surfacecontact with the finger portions of both of the switch contact elementsof said second unit whereby when pressure is applied bringing a portionof said two units closer together at least a pair of said fingerportions are bridged by. at least one of said bridging elements and lowresistance electrical contact is provided between said contact elements.

2. The device as recited in claim 1 and further including a flexiblejacket for encapsulating said units.

3. The device as recited in claim 1 wherein said first unit is segmentedto separate said bridging elements from each other thereby facilitatingthe independent movement of said bridging elements.

4. The device as recited in claim 1 wherein the bar portions of saidswitch contact elements run substantially parallel to each other andsaid finger portions extend substantially perpendicularly from said barportions.

5. The device as recited in claim 4 wherein said bridging elements runin a direction substantially parallel to the bar portions of said switchcontact elements.

6. The device as recited in claim 1 wherein said first unit isfabricated of a flexible material.

7. The device as recited in claim 1 wherein the finger portions of oneof said switch contact elements interleave with the finger portions ofthe other of said switch contact elements.

References Cited UNITED STATES PATENTS 2,044,080 6/ 1936 Kemper.2,896,042 7/1959 Koenig 20086 FOREIGN PATENTS 618,779 2/ 1949 GreatBritain.

ROBERT K. SCHAEFER, Primary Examiner.

D. SMITH, JR., Assistant Examiner.

US. Cl. X.R. 20052, 86

